Piano sounding board assembly



y 1957 c. ANDERSEN ET-AL 2 ,800,049

PIANO SOUNDING BOARDYASSEMBLY 3 Sheets-Sheet 1 Filed Oct.

c. ANDERSEN m AL 2,800,049

PIANO souunmc BOARD ASSEMBLY July 23, 1957 Filed Oct.

20. 1953 3 Sheets-Sheet 2 nwewra/c, (21/010 flzvi sbw y I ramve'rj July 23, 1957 Filed Oct, 20. 1955 C. ANDERSEN ET AL PIANO SOUNDING BOARD ASSEMBLY Q 5 Sheets-Sheet 3 INVENTORS. C2 zrroxn fl/varmscM emphasis of the basic fundamental tone.

United States Patent PIANO SOUNDING BOARD ASSEMBLY Clifford Andersen and Oscar Anderson, De Kalb, Il l., assignors to The Rudolph Wurlitzer Company, Chicago, 111., a corporation Application October 20, 1953, Serial No. 387,164

Claims. (Cl. 84- 187) This invention relates to an improvement in sounding boards, particularly applicable for use in upright pianos of the spinet type, it being the purpose of the invention to develop tone qualities in a sounding board of relatively small area comparable to that of the concert grand pianos.

It is, therefore, the object of this invention to provide such sounding board assembly resulting in improved tonal qualities aimed at lowering the basic fundamental sounding board tone and obtaining a gOod break note characteristic in the piano, and wherein the basic fundamental sounding board tone is increased and made more pronounced through the balancing of the sounding board such as to permit of the lower partials flowing longer in i To this end tapered sounding board ribs, the bass bridge structure and the treble bridge structure, including the relative direction of the grain, are all designed in relation to each other to propel the vibration from the bridge out into the open part of the board. This effects an improvement in the tone of the sounding board and, therefore, of the piano and results in even tone distribution.

The invention includes the form and arrangement of the bass bridge assembly relative to the sounding board in a manner to loosen the area near the bottom of the bridge where the bass strings are located, and to tighten the area near the top of the bridge. This results in the bridge oscillating as an entire unit, rather than as a pendulum with the top and oscillating freely.

The invention further includes the form and arrangement of the treble bridge assembly in a manner tending to loosen the board area around the lower end of the treble bridge and propel the sound energy toward the center of the board, resulting in a lowering of the basic fundamental sounding board tone. 7

The principal feature of the invention resides in the form and arrangement of the reinforcing ribs of the sounding board to improve the foundation for the sounding board and provide a greater gluing area, resulting in increased flexibility and improved termination of the board. Thus, the ribs are tapered to present a gradually increasing body to the board from the bottom thereof toward the pentagonal area, and are initially crowned to create a more even flow of the lower partials.

, Other features of the invention will be made to appear from the following specifications and claims.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a plan view of the sounding board with the string plate and strings mounted thereon.

Fig. 2 is the same as Fig. l with the string plate and strings removed.

Fig. 3 is an end elevation viewed from the line 33 bf Fig. 2.

*Fig. 4 is an exaggerated partial view of one of the ribs showing the crowned bottom side thereof.

Fig. 5 is an enlarged section taken on the line 55 of Fig. 2.

Fig. 6 is an enlarged section taken on the line 66 of Fig. 2.

In the drawings there is shown a sounding board 10 mounted upon and within the sounding board lining 11 and reinforced on its back face by a series of sounding board ribs 13. Glued to the front face thereof, as in the usual manner, there is a treble bridge 14 formed at the lower end thereof with an extension of substantial area and of particular formation which may herein be referred to as the calibrated element 15. Similarly glued to the front face of the board there is a bass bridge comprising a bass bridge runner 16 terminating at one end in a tail portion 17. Carried by the runner 16 there is a bass bridge plate 18 mounting a bass bridge cap 19.

Rigidly secured over the front face of the sounding board there is a metal string plate 20 reinforced by a series of ribs, such as indicated at 21, with intermediate portions removed to expose the bass and treble bridge and lighten the structure. Said plate is provided in the usual manner with groups of lower treble string pins 22 and upper treble string pins 23 to which the treble strings 24 are secured. Similarly, said plate is provided with the lower bass string pins 25 and upper bass string pins 26 for securing the series of bass strings 27, the treble strings extending to the right-hand side of Fig. 1 and the bass strings to the left-hand side thereof.

The treble bridge 14 extends downwardly toward the bass section terminating in overlying relation with the calibrated element 15. Said element comprises a thin wafer-like board glued firmly over the surface of the sounding board and lying under the lower terminal end of the treble bridge, being curved upwardly and thence rearwardly from the terminal end of the bridge so as to cover a substantial area of the board adjacent its lower edge but spaced therefrom substantially the distance of the terminal end of the treble bridge. The grain of said element is related to the grain of the sounding board so as to extend approximately five to ten degrees out of parallel therewith. This relation of the direction of the grain, as between the sounding board and the calibrated element, serves to loosen up the board area around the treble bridge and tends to propel the sound energy toward the center of the board.

It is the purpose of this design of treble bridge and its calibrated element to develop the basic fundamental tone of the sounding board so that it Will be the same at the point of contact of the calibrated element as it is at the top of the bass bridge to obtain a good break note characteristic in the piano. The basic fundamental tone at these points should be the same as the basic fundamental tone and flow of tone which is produced when the sounding board is struck in the center. By basic fundamental tone of the sounding board is meant the tone that is produced by striking the sounding board at its center before the plate and strings are attached. Thus, this structure is aimed at lowering the basic fundamental sounding board tone.

As shown in Fig. 2, the several ribs 13 terminate short of the sounding board lining instead of being notched and interlocked therewith as is customary. This creates a better foundation for the sounding board as well as a greater gluing area, resulting in increased flexibility and better termination of the sounding board. As shown in Fig. 6, the ribs are tapered throughout their lengths to provide a gradually increasing body to the board, from the bottom of the board to the pentagonal area. This structure creates a more even flow of the lower partials. For example, it is known that a maximum amplitude of the board area occurs in what has been termed the pentagonal feature.

To illustrate, oscillation of different areas of the board may be followed by the pencil test, wherein a pencil point is held loosely against the sounding board near the fourth rib, counting from the bass section or the left-hand side of the board as shown. Upon striking a note on the piano, preferably D above the break, the pencil may be moved slowly upwards toward the top of the sounding board and in contact therewith. The vibration will be readily felt, showing where and how much vibration occurs in the sounding board as the piano is played. From this test it will be found that the maximum oscillation occurs in the pentagonal feature and the minimum oscillation at the bottom of the board.

To further enhance this condition, the ribs are tapered so that the minimum of material of the rib is at the bottom of the sounding board and the maximum thickness of the rib is at the top of the sounding board. Since there is a fixed amount of energy created by a hammer blow, the balanced corner or pentagonal feature dissipates such energy of the board more slowly, thus sustaining the flow of the tone. The stiffening of this area improves the vibratory quality of the entire sounding board, as may be readily discernible by the above pencil test. Thus, the stronger fundamental tone quality of the piano is developed.

It may be further pointed out that in the prior sounding board structures the oscillation of the board was forced to occur more pronounced in the pentagonal feature. By the structure of this invention the efiiciency of this pentagonal feature is increased by spreading the oscillation and by improving the termination of the board in this particular area with respect to the build-up and decay characteristics of the piano. The tapered rib in conjunction with the form and structure of the calibrated element and bass bridge contributes to create a better balanced sounding board, due to the increased basic fundamental sounding board tone which is made more pronounced. Also, the lower partials are caused to flow longer and will emphasize the basic fundamental tone.

In this connection it may be stated that the sounding board has a definite effect on the tone quality of the entire instrument; the lower the pitch, within reason, the more the fundamental component of the string is emphasized. For example, the ideal sounding board can be compared to a broad band amplifier, which has no particular resonant frequency, but amplifies all frequencies at a constant amplitude. However, all diaphragms, such as a sounding board, must have a resonant frequency, and the maximum amplification will occur at this frequency. Thus, the sounding board assembly of this invention approaches the ideal conditions resulting in improved tone with more fundamental tone quality and a longer tonal flow.

For the above reasons it is desirable that the ribs 13 be initially crowned as shown in Fig. 6 along that surface 13a thereof adapted to be secured to the back face of the sounding board, and before gaining as indicated at 1312. The crowning of the underside of the ribs is indicated by the crown spacing indicated at A and B with respect to the plane indicated by dotted lines at C in Fig. 6. Each end of the rib is rounded off, as illustrated at 130 in Fig. 2, terminating short of the sounding board liner.

The invention claimed is:

l. A piano sounding board assembly secured to and within a lining extending thereabout adjacent the outer portion thereof, said board being of wood and having its grain structure extending diagonally upwardly from one edge of said board at the bass section towards the opposite edge of said board at the treble section, and a series of spaced wooden ribs secured to the back face of said board extending transversely of the grain thereof at an upwardly extending angle and tapering outwardly throughout their lengths from said first-mentioned edge of said board at the treble section toward the opposite edge of said board at the bass section, each of said ribs being glued to the back face of said board with their ends rounded and terminating short of and in spaced relation to said sounding board lining.

2. A piano sounding board assembly secured to and within a lining extending thereabout adjacent the outer portion thereof, said board being of wood and having its grain structure extending diagonally upwardly from one edge of said board at the bass section towards the opposite edge of said board at the treble section, and a series of spaced wooden ribs secured to the back face of said board extending transversely of the grain thereof at an upwardly extending angle and tapering outwardly throughout their lengths from said first-mentioned edge of said board at the treble section toward the opposite edge of said board at the bass section, each of said ribs being initially crowned along the surface thereof to be secured to the board and before securing thereto, whereby opposite ends of each rib will tend to bow upwardly from the normal plane thereof.

3. A piano sounding board assembly secured to and within a lining extending thereabout adjacent the outer portion thereof, said board being of wood having a pentagonal area and a grain structure extending diagonally from one edge of said board at the bass section towards the opposite edge of said board at the treble section, and a series of spaced wooden ribs secured to the back face of said board extending transversely of the grain thereof at an upwardly extending angle from said first-mentioned edge of said board at the treble section toward the opposite edge of said board at the bass section, each of said ribs being tapered along its free edge throughout the length thereof from a thicker portion to a thinner portion for presenting a gradually increasing body to the board from the bottom thereof toward the pentagonal area to create a more even flow of the lower partials.

4. A piano sounding board assembly secured to and within a lining extending thereabout adjacent the outer portion thereof, said board being of wood and having a pentagonal area, and a series of spaced wooden ribs secured at one edge to the back face of said board and extending at an angle to the bottom thereof, each of said ribs being tapered throughout its length along the edge remote from said board face to present a gradually increasing body to the sounding board from the bottom thereof toward the pentagonal area to create a more even flow of the lower partials.

5. A piano sounding board assembly secured to and within a lining extending thereabout adjacent the outer portion thereof, said board being of wood and having its grain structure extending diagonally upwardly from one edge of said board at the bass section towards the opposite edge of said board at the treble section, and a series of spaced wooden ribs secured to the back face of said board extending tranversely of the grain thereof at an upwardly extending angle and tapering outwardly throughout their lengths from said first-mentioned edge of said board at the treble section toward the opposite edge of said board at the bass section, each of said ribs being glued to the back face of said board with their ends rounded and terminating short of and in spaced relation to said sounding board lining, and each of said ribs being initially crowned along the surface thereof to be secured to the board and before securing thereto, whereby opposite ends of each rib will tend to bow upwardly from normal plane thereof.

References Cited in the file of this patent UNITED STATES PATENTS 66,653 Trayser July 9, 1867 1,164,005 Mehlin Dec. 14, 1915 1,299,203 Meinzolt Apr. 1, 1919 1,699,561 Collen Ian. 22, 1929 (Other references on following page) Mehlin Mar. 12, 1929 Disler Sept. 10, 1929 Loar Mar. 31, 1931 Loar July 21, 1931 Fischer Jan. 14, 1936 Male Feb. 23, 1937 6 Schimmel Apr. 30, 1940 Bronson May 14, 1940 FOREIGN PATENTS Germany May 8, 1905 Great Britain Aug. 23, 1923 France Dec. 10, 1926 Australia Apr. 10, 1928 

